| Title | Experiences from use of TRT (Thermal Response Test) in the design praxis for BHE (Borehole Heat Exchanger): lessons learned, enhanced information, new developments |
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| Authors | Sauer, M; Mands, E; Grundmann, E; Sanner, B |
| Year | 2016 |
| Conference | European Geothermal Congress |
| Keywords | borehole heat exchangers, design, Thermal Response Test, test equipment, evaluation, improvements |
| Abstract | Mobile TRT (Thermal Response Test) equipment was developed 20 years ago in USA and Sweden. Through cooperation within IEA-projects the idea soon spread to other countries, and today is applied in every region where a certain market for ground source heat pumps exists. Over the years a wealth of experience could be collected, and development lead to substantial improvements, however, some experience also helped to understand what not to do. The data collection during TRT, and the information derived from TRT data, improved considerably with better equipment and increasing experience. Proper data collection is only one part of TRT, the other, and equally important, is data evaluation. Evaluation today has little in common with that of the 1990, beside some basic mathematical rules. Parameter estimation techniques are widely used today, allowing for evaluation of tests with additional influences (variable load over time, groundwater, etc.). Temperature logs help to understand the lithological and hydrogeological setting and yield valuable additional information. The usefulness of TRT meanwhile is not only proven for determination of underground thermal conductivity, but also for other parameters like determining length of borehole heat exchangers, existence of grouting in the annulus, presence of moving groundwater, etc. The paper, however, limits the scope to the type of TRT used commercially for design of borehole heat exchangers, and does not cover variations in test operation and evaluation used in R&D, mainly to understand the basic operation of ground heat exchangers. |